OpenID is an open standard that describes how users can be authenticated in a decentralized manner, obviating the need for services to provide their own ad hoc systems and allowing users to consolidate their digital identities

The OpenID protocol does not rely on a central authority to authenticate a user's identity. Moreover, neither services nor the OpenID standard may mandate a specific means by which to authenticate users, allowing for approaches ranging from the common (such as passwords) to the novel (such as smart cards or biometrics).